Temperature requirements for the germination of alternative forage species for northern New Zealand climates and a prominent weed

Abstract

Ryegrass-clover pastures are increasingly facing challenges with reduced persistence and weed ingress, especially in northern New Zealand dairying regions. Seed germination is the first, and arguably most important step, to determine the successful establishment of pasture (or weed) species. Soil temperature and soil moisture are important factors for germination and therefore determining species specific preferences for these parameters can indicate the environmental conditions facultative to their establishment. This study aimed to determine the cardinal germination temperatures of four forage cultivars: Haven tall fescue (Lolium arundinaceum(Schreb.) Darbysh.), Oakdon meadow fescue (Lolium pratense (Huds.) Darbysh.), berseem clover (Trifolium alexandrinum L.) and Fulkerson kikuyu (Cenchrus clandestinus (Hochst. ex Chiov.) Morrone) and one prominent weed: Madagascar ragwort (Senecio madagascariensis Poir.) relevant to northern pastures. Seeds were germinated across a range of temperatures for 28 days and cardinal temperatures were determined
using broken-stick models. Cardinal temperatures and thermal time requirements are reported in the text. Kikuyu has a high base temperature for germination, which suggests a slow germination rate in spring compared to temperate forages, limiting its use in regions below the northern North Island. Madagascar ragwort has similar temperature requirements to ryegrasses and fescues. Further study of the interaction between soil temperature and moisture (hydrothermal constraints) would increase understanding of the germination behaviour of these species.